Many types of input devices are presently available for performing operations in a computing system, such as buttons or keys, mice, trackballs, touch panels, joysticks, touch screens and the like. Touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as their declining price. Touch screens may include a touch panel, which may be a clear panel with a touch-sensitive surface. The touch panel may be positioned in front of a display screen so that the touch-sensitive surface covers the viewable area of the display screen. Touch screens may allow a user to make selections and move a cursor by simply touching the display screen via a finger or stylus. In general, the touch screen may recognize the touch and position of the touch on the display screen, and the computing system may interpret the touch and thereafter perform an action based on the touch event.
One limitation of many conventional touch panel technologies is that they are only capable of reporting a single point or touch event, even when multiple objects come into contact with the sensing surface. That is, they lack the ability to track multiple points of contact at the same time. Thus, even when two points are touched, these conventional devices only identify a single location, which is typically the average between the two contacts (e.g. a conventional touchpad on a notebook computer provides such functionality). This single-point identification is a function of the way these devices provide a value representative of the touch point, which is generally by providing an average resistance or capacitance value.
Moreover, a concern with many touch devices is the amount of power they consume when actively scanning a touch sensor panel. The high power consumption problem may be particularly important for hand-held devices, as a hand-held device's limited power supply can be readily consumed by actively scanning the touch sensor panel as well as processing those scans. These scans can be wasteful if there is no touch-activity on the panel for an extended period of time.
A possible remedy for a loss of power consumption during periods of inactivity is to shut down (i.e. turn off) the touch panel or touch panel device. But doing so can have several disadvantages, such as consuming even more power when turning the touch panel back on (particularly if the period of inactivity is not an extended period of time) and the inconvenience to the user for having to wait for the touch panel to turn back on. Additionally, a user may forget to turn the touch panel off, so the device continues to actively scan the touch panel despite the user is not inputting any touch data.